A 14,000-year environmental change history revealed by mineral magnetic data from White Lake, New Jersey, USA

Abstract

The increasing use of magnetic parameters as a proxy for environmental change necessitates the understanding of processes that link magnetic properties of sediments, especially organic-rich lake sediments, and environmental change. To explore the magnetic mineral-paleoenvironment link, we have recovered a 14,000 yr mineral-magnetic record from White Lake, a hardwater lake containing organic-rich sediments in northwestern New Jersey, USA. Pre-14 ka (1 ka = 1000 cal yr BP) sediments are dominated by clays, and the magnetic variations of the clays recorded the deglaciation process, the initial development of the lake, and the stabilization of the watershed. The rapid increase in organic matter and carbonate around 14 ka likely marks the Bølling warming event. The marl sediments were deposited from 14 to 11 ka and displayed a continued decline in magnetic mineral concentration, which indicates increasing marl precipitation in the lake and stabilization of the watershed by vegetation growth. The Holocene gyttja-dominated sediments generally have weak magnetizations. However, yellowish marl layers in the Holocene sediments display strong magnetizations. The strong magnetization of marl layers at ∼ 1.3, 3.0, 4.4, and 6.1 ka probably resulted from oxidation of the precipitated marl sediments near to shore, which were then eroded, transported, and redeposited during periods of low lake levels. This study demonstrates that multiple magnetic parameters can provide a more detailed and robust interpretation of environmental change than lithologic data alone.